1. Field of the Invention
The present invention relates to compositions and methods for solidifying agglomerations of solid and liquid waste materials and to methods of disposing waste materials such as drilling muds and cuttings that result from the drilling of oil and gas wells.
2. Description of the Prior Art
Liquid drilling fluid or drilling mud is an essential part of most oil and gas drilling operations. The mud is continuously circulated through the drill pipe, out through the drill bit and back to the surface through the annulus between the drill pipe and the casing. It serves to lubricate and cool the drill bit as the drill bit breaks up rock at the bottom of the hole, and it carries the rock cuttings to the surface. The mud also helps control pressures that exist in formations penetrated by the drill bit, stabilizes the hole by sheathing the wall of the hole and serves as a valuable source of downhole information.
When mud that has been circulated through the well reaches the surface, it is usually conducted through certain solids removal equipment such as shale shakers and settling tanks and then recirculated through the well. Eventually, the mud wears out and must be replaced by new mud. The used mud, together with drill cuttings and other material brought to the surface by the mud, is typically discharged into a pit that has been excavated adjacent the well. At the conclusion of the drilling operation, the agglomeration of mud and other materials in the pit must be disposed of so that the well site can be restored to a proper condition.
Disposing of the agglomeration of mud and other materials in the pit has not been an easy task. The agglomeration of materials usually exists in the form of a semisolid slurry that has no significant stability. Inasmuch as the materials usually involve brine and other potential contaminants and tend to leach and flow out of the area in which they are contained, they cannot be simply dumped on or spread out over the well site. As a result, several methods of disposing of the drilling mud and other materials agglomerated in mud pits have been developed.
A widely used method of disposing of drilling mud and other materials agglomerated in mud pits comprises the step of burying the agglomeration of materials directly on the well site. In carrying out this method, the pits are first allowed to settle for approximately one week. Free water standing in the pits is then removed and hauled to salt water disposal wells. Deep lateral trenches are excavated adjacent the pit and a portion of the soupy agglomeration of mud and other materials in the pit is allowed to flow into the trenches. The original pit and lateral trenches are then filled with dirt. Although this method may allow the surface of the land to be restored to an acceptable condition, it is not always environmentally safe. The buried materials can ooze or leach from the pit and adjacent trenches and contaminate the surrounding soil and ground waters.
Drilling mud and other materials agglomerated in mud pits have also been disposed of by hauling the materials to an approved landfill. A in the first method described above, the pits are first allowed to settle and free water is removed therefrom. The remaining materials in the pits are loaded onto dump trucks with a backhoe and trucked to the landfill site. This method is very costly and is generally used only in states where it is required.
Other methods of disposing of drilling muds and other materials agglomerated in mud pits include the step of solidifying or rigidifying the materials in the pits and then either hauling the materials away or burying them directly in the pits. In U.S. Pat. No. 4,460,292 issued July 17, 1984, a method is disclosed in which biogenetic silica such as rice hull ash is added by itself or together with additives to the mud and other materials in the pit to transform the mud and other materials into a solid or semi-solid mass so that they can be removed from the pit and hauled away. In U.S. Pat. No. 4,668,128 issued May 26, 1987, a method is disclosed in which hydroscopic powder and a cementitious binder are admixed with the mud and other materials in the pit to produce a rigid, form-stable matrix. The matrix is then buried in the pit.
The methods in which mud and other materials agglomerated in the pit are solidified or rigidified result in less contamination than the other methods of disposing of drilling mud and other materials developed heretofor. Such methods can be very economically carried out if the solidified or rigidified agglomeration of drilling mud and other materials can be buried directly on the well site.
By the present invention, an improved waste solidification composition is provided. The composition very effectively solidifies drilling mud and other materials agglomerated in a mud pit during the drilling of an oil and gas well. The solidified agglomeration of mud and other materials can be buried directly in the pit, thereby eliminating the cost of hauling the agglomeration away.